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求助TT GWD 11-27 一道阅读题目~
Q24 to Q27:
Anole lizard species that
occur together (sympatrically)
on certain Caribbean islands
Line occupy different habitats:
(5) some live only in the grass,
some only on tree trunks, and
some only on twigs. These
species also differ morpho-
logically: grass dwellers are
(10) slender with long tails, tree
dwellers are stocky with long
legs, twig dwellers are slender
but stubby-legged. What is
striking about these lizards
(15) is not that coexisting species
differ in morphology and habi-
tat use (such differences are
common among closely related
sympatric species), but that
(20) the same three types of habi-
tat specialists occur on each
of four islands: Puerto Rico,
Cuba, Hispaniola
, and Jamaica.Moreover, the Puerto Rican
(25) twig species closely resembles
the twig species of Cuba,
Hispaniola, and Jamaica
inmorphology, habitat use, and
behavior. Likewise, the spe-
(30) cialists for other habitats are
similar across the islands.
The presence of similar
species on different islands
could be variously explained.
(35)
An ancestral species might
have adapted to exploit a
particular ecological niche on
one island and then traveled
over water to colonize other
(40) islands. Or this ancestral
species might have evolved
at a time when the islands
were connected, which some
of these islands may once
(45) have been. After the islands
separated, the isolated lizard
populations would have become
distinct species while also
retaining their ancestors’ niche
(50) adaptations. Both of these
scenarios imply that speciali-
zation to each niche occurred
only once. Alternatively, each
specialist could have arisen
(55) independently on each of the
islands.
If each type of specialist
evolved just once, then similar
specialists on different islands
(60) would be closely related.
Conversely, if the specialists
evolved independently on each
island, then a specialist on one
island would be more closely
(65) related to other types of anoles
on the same island—regardless
of their ecological niches—
than it would be to a similar
specialist on a different island.
(70) Biologists can infer how
species are related evolu-
tionarily by comparing DNA
sequences for the same genes
in different species. Species
(75) with similar DNA sequences
for these genes are generally
more closely related to each
other than to species with less-
similar DNA sequences. DNA
(80) evidence concerning the anoles
led researchers to conclude
that habitat specialists on one
island are not closely related
to the same habitat specialists
(85) elsewhere, indicating that spe-
cialists evolved independently
on each island.
Q27:
The passage suggests that if a grass-dwelling anole lizard species evolved on one island and then traveled over water to colonize a second island, the grass-dwelling anoles on the two islands would eventually
- develop very different DNA sequences
- develop into different species that are more distantly related to each other than to tree- and twig-dwelling anoles on their own islands
- come to differ significantly from one another in habitat use
- develop into different, but closely related, species
- evolve significant morphological differences
这道题老是想不明白,各位NN们帮忙指点一下啊~~多谢多谢~~~
答案是D,但是我觉得文中明确又说两者并不是closely related,所以我没有选择D。而后我认为文章中并没有讲到说同一个岛上的不同生物的联系可以比不同岛上的由同一生物发展而来的不同生物之间的联系更紧,所以我也没有选B。倒是觉得最后一段里面主要讲了最初一个生物由于去了不同的岛,但是由于independently发展,所以不再closely related, 又根据Species with similar DNA sequences for these genes are generally more closely related to each other than to species with less-similar DNA sequences,觉得应该是具有different DNA sequences... |
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